Introduction: Omental infarction is a rare cause of acute abdominal pain. It is classified into two categories, primary and secondary omental infarction according to existence of identifiable etiology such as intra-abdominal pathology and thrombosis due to various causes. Primary omental infarction is known to be associated with obesity, local trauma, heavy food intake, excessive exercise, coughing, sudden changes in position. Omental infarction appears to be a self-limiting disease. However, surgery may be needed if there are deteriorating symptoms, signs or clinical markers. Since omental infarction has a non-specific symptoms, it is difficult to diagnose and manage. Therefore, we share our experience of a primary omental infarction case in a 7-year-old-girl. Case: A previously healthy 7-year-old girl admitted to hospital due to severe right upper quadrant abdominal pain which developed 2 days ago. There was no other symptoms like fever, vomiting or diarrhea. Abdomen was soft and flat with focal tenderness on right upper quadrant. She had no history of operation or trauma. In the laboratory evaluation, WBC count was 16,700/uL, CRP was 49.33 mg/L, and the rest were within normal range. Abdominal ultrasonography shows approximately 3.9x1.9x4.6 cm sized hyper-echoic lesion with slight bulging contour in the omental fat with decreased color flow at right upper quadrant abdomen, highly suggestive of omental infarction. After consultation to Pediatric surgery department, we decided to start antibiotics (Cefotaxime 200mg/kg/day). 1 week after admission, Abdominal pain was subsided and follow-up laboratory findings were improved. Conclusion: There are various causes of abdominal pain in children and omental infarction can be a rare one. Therefore omental infarction should be in consideration while managing patient with acute abdomen. We recommend to consider abdominal ultrasonography which can be a diagnosis of choice to figure out the cause of atypical abdominal pain in children.